Problem: Using the van't Hoff factors in the table below, calculate the mass of solute required to make each aqueous solution.Van't Hoff factors at 0.05 m concentration in aqueous solutionSoluteExpectedMeasuredNonelectrolyte11NaCl21.9MgSO421.3MgCl232.7K2SO432.6FeCl343.4Calculate the mass of solute required to make a sodium chloride solution containing 161 g of water that has a melting point of -1.9 oC.

FREE Expert Solution

Recall that the freezing point of a solution is lower than that of the pure solvent and the change in freezing point (ΔT­f) is given by:


ΔTf=Tf, pure solvent-Tf, solution


The change in freezing point is also related to the molality of the solution:


ΔTf=imKf


where: 

i = van’t Hoff factor

m = molality of the solution (in m or mol/kg)

Kf = freezing point depression constant (in ˚C/m)


Recall that the molality of a solution is given by:


molality=moles solutekg solvent


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Problem Details
Using the van't Hoff factors in the table below, calculate the mass of solute required to make each aqueous solution.
Van't Hoff factors at 0.05 m concentration in aqueous solution
SoluteExpectedMeasured
Nonelectrolyte11
NaCl21.9
MgSO421.3
MgCl232.7
K2SO432.6
FeCl343.4

Calculate the mass of solute required to make a sodium chloride solution containing 161 g of water that has a melting point of -1.9 oC.

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